The present invention is directed to bicycle shift control devices and, more particularly, to a shift control device having a compact design to facilitate mounting the shift control device in close proximity to other structures.
Twist-grip shift control devices are sometimes used to control various types of bicycle transmissions. Examples of such devices are disclosed in U.S. Pat. No. 3,633,437 and U.S. Pat. No. 5,197,927. Each device disclosed in those patents includes a rotatable handgrip mounted around the handlebar coaxially with the handlebar axis, a pulley inclined relative to the rotatable handgrip for winding a transmission cable, and a motion transmitting structure for transmitting motion of the rotatable handgrip to the pulley. In the device disclosed in U.S. Pat. No. 3,633,437, the motion transmitting member is a pair of bevel gears formed by the peripheral surfaces of the rotatable handgrip and the pulley. The device disclosed in U.S. Pat. No. 5,197,927 also employs a pair of bevel gears formed by the peripheral surfaces of the rotatable handgrip and the pulley. Alternatively, that device may employ a connecting cable connected between the rotatable handgrip and the pulley.
When a connecting cable is used to transmit motion between the rotatable handgrip and the pulley, the pulley typically must have two winding grooves-one for the cable controlling the bicycle transmission and another one for the cable coupling the pulley to the rotatable handgrip. The winding grooves usually are located on an outer peripheral surface of the pulley. The end of each cable is fitted with a terminating nipple that is fitted within a recess formed in the pulley. The pulley ordinarily has a thickness sufficient to accommodate two nipples aligned end to end, even though the two nipples are not always positioned adjacent to each other, in order to provide sufficient support and rigidity for the two cable nipples. However, such a thickness increases the size of the shift control device, thus making the shift control device aesthetically unappealing, and it makes it difficult to mount the shift control device in close proximity to other devices, such as a brake lever assembly.
Another problem with conventional twist-grip shifting devices is that the overall structure of such devices does not allow other control devices to be efficient mounted adjacent to them because the housing of the shifting device usually extends perpendicular to the handlebar, and the pulley is located almost immediately adjacent to the handlebar. As a result, the other control device must be located laterally of the pulley, far away from the rider's hand, which makes the control device difficult if not impossible to operate. Some devices may be mounted adjacent to the housing, but this, too, tends to locate the other control device further from the rider's hand than is desirable.